EP0645381B1 - Mehrstufiges Verfahren zum Trocknen und Reinigen von Propylenoxid - Google Patents

Mehrstufiges Verfahren zum Trocknen und Reinigen von Propylenoxid Download PDF

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EP0645381B1
EP0645381B1 EP94306848A EP94306848A EP0645381B1 EP 0645381 B1 EP0645381 B1 EP 0645381B1 EP 94306848 A EP94306848 A EP 94306848A EP 94306848 A EP94306848 A EP 94306848A EP 0645381 B1 EP0645381 B1 EP 0645381B1
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Prior art keywords
distillation
propylene oxide
fraction
distillation column
extractive
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French (fr)
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EP0645381A1 (de
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Mark Elliott Taylor
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Huntsman Specialty Chemicals Corp
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Huntsman Specialty Chemicals Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
    • B01D3/40—Extractive distillation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14—Fractional distillation or use of a fractionation or rectification column
    • B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
    • B01D3/146—Multiple effect distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/32—Separation; Purification

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  • This invention relates to the plural stage drying and purification of propylene oxide. More particularly, this invention relates to a plural stage distillation process for removing contaminating quantities of impurities, including water, from propylene oxide. Still more particularly, this invention relates to a plural stage distillation process for the purification of impure propylene oxide contaminated with impurities such as water, propylene, propane, acetaldehyde, methyl formate, propionaldehyde, hexenes, acetone, hexanes, methanol, t-butyl alcohol, pentane, isopentane, pentenes, isopropyl alcohol and t-butyl formate.
  • impurities such as water, propylene, propane, acetaldehyde, methyl formate, propionaldehyde, hexenes, acetone, hexanes, methanol, t-butyl alcohol, pentane, isopentane, pentenes,
  • the impure propylene oxide is distilled by a plural stage process using a C 2 to C 6 alkylene glycol extractive distillation agent in a first drying stage and a terminal drying stage and a C 7 to C 10 alkane hydrocarbon extractive distillation agent for intermediate purification stages.
  • alkane hydrocarbons containing 6 to 18 carbon atoms as extractive distillation agents in the purification of propylene oxide. See, for example, Binning et al. U. S. Patent No. 3,338,800, Jubin U. S. Patent No. 3,464,897, Jubin U. S. Patent No. 3,607,669 and Schmidt U. S. Patent No. 3,843,488. Jubin U. S. Patent No. 3,464,897 shows that an alkane such as octane is effective for the removal of 6 carbon atom alkane impurities such as 2-methyl pentane, 4-methyl pentene-1, 2-methyl pentene-1 and 2-methyl pentene-2. Schmidt U. S. Patent No.
  • 3,843,488 shows that alkanes containing from 8 to 20 carbon atoms, and preferably from 8 to 10 carbon atoms, such as n-octane, is effective for removing hydrocarbon impurities containing 5 to 7 carbon atoms from propylene oxide.
  • Washall U. S. Patent No. 3,578,568 discloses the use of ethylene glycol and propylene glycol as extractive agents for the purification of propylene oxide. Kageyama et al.
  • U. S. Patent No. 3,838,020 discloses the use of butylene glycols for this purpose. Shih et al. U. S. Patent No. 5,000,825 discloses the use of glycols containing 2 to 4 carbon atoms such as ethylene glycol, propane diol, butane diol, etc. Marquis et al. U. S. Patent No. 5,139,622 discloses the use of triethylene glycol as an extractive distillation agent and Marquis et al. U. S. Patent No. 5,160,587 discloses the use of dipropylene glycol as an extractive distillation agent.
  • Schmidt U. S. Patent No. 3,881,996 discloses a plural stage process for the purification of propylene oxide including a first fractionation wherein light impurities such as acetaldehyde are removed overhead followed by a second distillation step wherein heavy impurities such as propionaldehyde are removed in order to provide a second distillate fraction which is then extractively distilled in the presence of octane in a third distillation zone to provide pure propylene oxide and to remove alkane hydrocarbon impurities such as C 6 carbon atom impurities from the propylene oxide.
  • Schmidt et al. teach that it is important to use the proper sequence of distillation steps and that, for example, removal of heavy impurities such as propionaldehyde before the removal of light impurities such as acetaldehyde will lead to adverse results.
  • Shih U. S. Patent No. 5,133,839 discloses a plural stage process for the purification of propylene oxide utilizing a conventional distillation zone which preferably contains two distillation columns, as in Schmidt U. S. Patent No. 3,881,996, followed by extractive distillation of the parts of purified propylene oxide in two sequential extractive distillation columns using either isooctane or a lower alkylene glycol as the extractive distillation agent and removing lighter impurities in the first of the extractive distillation columns and heavier impurities from the second of the extractive distillation columns.
  • EP-A-0624578 has an earlier priority date than the present disclosure and is prior art pursuant to Article 54(3) and (4) EPC for all designated States.
  • EP-A-0624578 discloses water, hydrocarbons and oxygen-containing impurities which can be separated from impure propylene oxide in a sequence of distillation steps, wherein
  • Pentanes and pentenes are present in crude propylene oxide as minor impurities. The removal of pentanes and pentenes presents a difficult problem.
  • Pentanes, isopentane and pentenes may be removed like other hydrocarbon impurities by using a C 8 -C 10 alkane in an extractive distillation.
  • the C 8 -C 10 alkane solvent lowers the relative volatility of the hydrocarbons relative to propylene oxide. However, the degree of relative volatility change is proportional to the amount of solvent present.
  • a more economical and efficient means of removing pentanes and pentenes is by a distillation upstream of the C 8 -C 10 alkane extractive distillation.
  • the C5 stripper tower should not be located downstream of the C 8 -C 10 extractive distillation since the final PO product would then be a bottoms product off the stripper. It is advantageous to take high purity products off the top of columns rather than off the bottom.
  • partial drying of the propylene oxide and substantially complete removal of the C 5 hydrocarbons is accomplished in the first stage of the plural distillation process utilizing a C 2 -C 6 alkylene glycol extractive distillation agent.
  • crude propylene oxide is separated from contaminating quantities of water, hexanes, hexenes, pentanes, pentenes, and oxygen-containing impurities by a sequential extractive distillation process wherein the crude propylene oxide is first extractively distilled using a lower alkylene glycol extractive distillation agent to form a first partially dehydrated overhead fraction comprising propylene oxide, water, hexanes, hexenes, pentanes and pentenes and oxygen-containing impurities boiling above propylene oxide, wherein the first overhead distillation fraction is separated in a second distillation column into a second overhead distillation fraction comprising most of the pentanes, pentenes, oxygen-containing impurities boiling above propylene oxide and a residual amount of propylene oxide and a second partially purified propylene oxide bottoms fraction comprising propylene oxide, water, hexenes, hexanes and only residual quantities of pentenes and pentanes, wherein the partially
  • the propylene oxide overhead fraction consisting essentially of propylene oxide and water is charged to a terminal distillation stage where it is dehydrated utilizing an extractive distillation agent consisting essentially of a C 2 to C 6 alkylene glycol extractive distillation agent to provide a final overhead distillate fraction consisting essentially of anhydrous purified propylene oxide.
  • impure propylene oxide contaminated with water, pentanes, pentenes, hexenes, hexanes and oxygen-containing impurities is purified by a sequential extractive distillation process wherein (a) the impure propylene oxide is extractively distilled using a first C 2 to C 6 alkylene glycol extractive distillation agent to form a first lighter distillation fraction containing all of the propylene oxide, less than 50 wt.% of the water, hexenes, hexanes, pentenes and pentanes and oxygen-containing impurities boiling above propylene oxide and a first heavier distillation fraction containing more than 50 wt.% of the water and oxygen-containing impurities boiling above propylene oxide, including acetone, tertiary butyl alcohol, methanol and isopropyl alcohol, and all of the first extractive distillation agent, wherein (b) the first lighter distillation fraction is separated in a second distillation column
  • a distillation process for the purification of crude propylene oxide contaminated with water, propylene, propane, acetaldehyde, methyl formate, propionaldehyde, hexenes, acetone, hexanes, methanol, t-butyl alcohol, pentane, isopentane, pentenes, isopropyl alcohol and t-butyl formate comprising the steps of:
  • the drawing is a schematic flow sheet with conventional parts omitted showing the general recovery sequence that is used in accordance with the present invention to purify propylene oxide.
  • FIG. 1 a schematic flow sheet illustrating a preferred method for practicing the process of the present invention.
  • conventional parts such as valves, pumps, temperature sensors, pressure sensors, heaters, coolers, flow control regulation apparatus, reboilers and reflux condensers have been omitted.
  • the crude or impure propylene oxide to be purified in accordance with the present invention is typically propylene oxide prepared by the reaction of tertiary butyl hydroperoxide with propylene in the presence of a molybdenum catalyst to provide a reaction mixture comprising unreacted propylene, unreacted tertiary butyl hydroperoxide, tertiary butyl alcohol, propylene oxide, and impurities.
  • This reaction product is separated in a distillation zone (not shown) into a plurality of fractions including a propylene recycle fraction, a crude propylene oxide fraction, a tertiary butyl alcohol fraction and a residue fraction.
  • the crude propylene oxide obtained in this fashion is suitably used as a feedstock for the present invention and will normally be contaminated with impurities including water, propylene, propane, acetaldehyde, methyl formate, propionaldehyde, hexenes, acetone, hexanes,. methanol, tertiary butyl alcohol, pentane, isopentane, pentenes, isopropyl alcohol and tertiary butyl formate.
  • the impure propylene oxide will normally contain from about 97 to about 99 wt.% of propylene oxide, the balance being impurities such as those enumerated above. It will be understood that some of the enumerated impurities will not always be present in impure propylene oxide and that other impurities not listed may be present in minor quantities.
  • the impurities broadly speaking, comprise water, hydrocarbons such as propylene, propane, hexenes, hexanes, pentane, isopentane and pentenes, and oxygenated impurities including aldehydes, alcohols and esters.
  • the hydrocarbon impurities will normally contain from 2 to 6 carbon atoms and the oxygenated impurities will normally contain from 1 to 6 carbon atoms.
  • a crude propylene oxide of the type described is charged to a first extractive distillation column 10 by way of a charge line 12.
  • the fractional distillation column 10 may suitably comprise from 40 to 80 theoretical trays and the charge line 12 for the impure propylene oxide will normally be at least 10 to 30 trays from the bottom of the distillation tower.
  • the impure propylene oxide which will suitably comprise about 98.5 wt.% propylene oxide, the balance being impurities as mentioned above, may be charged at a temperature of 38°C (100°F) to 71°C (160°F).
  • the alkylene glycol extractive distillation agent suitably may be an alkylene glycol containing from 2 to 6 carbon atoms such as ethylene glycol, propylene glycol, 1,4-propane diol, 1,4-butane diol, 2-methyl-1,3-propane diol, diethylene glycol, triethylene glycol, dipropylene glycol.
  • Preferred extractive distillation agents include triethylene glycol and dipropylene glycol.
  • the alkylene glycol extractive agent 56 will suitably be charged to the extractive distillation column 10 in the ratio of 2 to 7 parts of crude propylene oxide per part of alkylene glycol extractive distillation agent.
  • Extractive distillation conditions are adjusted in the extractive distillation tower 10 so as to provide for the recovery as overhead or as a distillate fraction 16 of substantially all of the propylene oxide charged to the extractive distillation column 10.
  • the temperature at the bottom of the extractive distillation column 10 may suitably be 150°C - 200°C, and the pressure may be 140 - 345 kPa.
  • the temperature at the top of the extractive distillation column 10 may, for example, be 26°C - 50°C and the pressure may suitably be 105 - 175 kPa.
  • a first lighter distillation fraction comprising impure propylene oxide is removed from the column 10 by way of a line 16 and may suitably comprise more than 99 wt.% propylene oxide, the balance being impurities including acetaldehyde, methyl formate, hexenes, hexanes, methanol, water, pentanes, isopentanes and pentenes.
  • a heavier distillation fraction 18 discharged adjacent the bottom of the extractive distillation column 10 will comprise the alkylene glycol extractive distillation agent and impurities including water, propionaldehyde, acetone, methanol, tertiary butyl alcohol, isopropyl alcohol and tertiary butyl formate.
  • a second feedstock comprising the first lighter distillation fraction 16 is charged to a second distillation column 20 which may suitably contain from 20 to 40 theoretical trays, the second feedstock being suitably charged to 8 to 16 theoretical trays from the bottom of the tower.
  • Distillation conditions are adjusted in the distillation column 20 to provide a second lighter distillation fraction discharged by way of a line 22 and a second heavier partially purified distillation fraction discharged by a line 24.
  • Distillation conditions are suitably adjusted in the distillation column 20 so that substantially all of the propylene oxide will be present in the second heavier distillation fraction 24.
  • the lighter distillation fraction 22 will comprise impurities including propylene, propane, acetaldehyde and, significantly, substantially all of the pentanes and pentenes charged to the distillation column 20.
  • the second heavier distillation fraction 24 will typically contain heavier oxygen-containing impurities, water, substantially all of the propylene oxide, hexenes and hexanes.
  • a third feedstock comprising the second heavier distillation fraction 24 is charged to a third distillation column 30 together with a C 8 to C 10 alkane hydrocarbon extractive distillation agent which is charged by a line 32.
  • the alkane extractive distillation agent may suitably be charged to the third distillation column 30 in the ratio of 5 to 7 parts of extractive distillation agent per part of third feedstock 24. Extractive distillation conditions are adjusted in the distillation column 30 to provide for a third heavier distillation fraction 33 containing water, substantially all of the propylene oxide, hexenes and hexanes and a lighter distillation fraction 34 which will typically comprise impurities such as methyl formate, acetaldehyde, water and methanol. Residual quantities of propylene oxide and hexane may also be present.
  • the extractive distillation agent charged to the distillation column 30 is suitably an 8-10 carbon atom alkane such as normal octane or isooctane.
  • the third feedstock 24 charged to the third distillation column 30 may be suitably charged at a temperature of 54°C - 82°C.
  • the temperature at the bottom of the extractive distillation column 30 may suitably be 82°C - 105°C and the pressure may suitably be 200 - 345 kPa.
  • the temperature adjacent the top of the extractive distillation tower 30 may suitably be 55 - 71°C and the pressure may suitably be 140 - 275 kPa.
  • a fourth feedstock comprising the third heavier distillation fraction 33 is charged to a fourth extractive distillation tower 40 together with an alkane extractive distillation agent such as a C 8 to C 10 alkane which is charged by way of a line 42.
  • the extractive distillation agent 42 may be charged to the extractive distillation column 40 in the ratio of 0.4 to 0.8 parts of extractive distillation agent per part of fourth feedstock 33.
  • Distillation conditions are adjusted in the distillation column 40 to provide lighter distillation fraction 44 consisting essentially of water and propylene oxide and a heavier distillation fraction 46 comprising the hexenes, hexanes and the extractive distillation agent.
  • the temperature at the top of the distillation column 40 may be 38°C - 55°C and the pressure may be 70 - 200 kPa.
  • the temperature adjacent the bottom of the distillation column 40 may suitably be 120°C - 144°C and the pressure may suitably be 175 - 310 kPa.
  • a fifth feedstock comprising the fourth lighter distillation fraction 44 is charged to a fifth (terminal) extractive distillation tower 50 together with a C 2 to C 6 alkylene glycol extractive distillation agent which is charged by a line 62.
  • the alkylene glycol extractive distillation agent 62 will suitably be charged to the extractive distillation column 50 in the ratio of 4 to 6 parts of the fifth feed-stock 44 per part of alkylene glycol extractive distillation agent.
  • Extractive distillation conditions are adjusted in the extractive column 50 so as to provide for the recovery of a lighter distillate fraction 52 consisting essentially of propylene oxide and substantially completely free from water.
  • the temperature at the bottom of extractive distillation column 50 may suitably be from 82°C - 105°C and the pressure may be from 140 kPa - 345 kPa.
  • the temperature at the top of the extractive distillation column 50 may, for example, be within the range of 30°C - 50°C and the pressure may suitably be from 105 kPa - 175 kPa.
  • a heavier distillation fraction 56 discharged from adjacent the bottom of extractive distillation column 50 will comprise water, the alkylene glycol extractive distillation agent, and propylene oxide.
  • the fifth distillation column 50 may suitably comprise 10 to 40 theoretical trays and the charge line 44 will suitably be at least 5 to 20 trays from the bottom of the distillation tower 50.
  • the heavier distillation fraction 56 which comprises the alkyl glycol extractive distillation agent and propylene oxide is charged to the first distillation column 10 in order to provide for the extractive distillation agent required therein and in order that the propylene oxide contained therein may be recovered by overhead line 16.
  • a sixth feedstock comprising the first heavier distillation fraction 18 from the first distillation column 10 may be charged to a sixth distillation column 60 containing from 20 to 60 theoretical trays wherein the sixth feedstock may be separated under distillation conditions adjusted to provide for the recovery of substantially all of the alkylene glycol extractive distillation agent as a heavier distillation fraction discharged from the distillation column 60 by a line 62 and a lighter distillation fraction 64 discharged from the distillation column 60 and containing propylene oxide, water, acetone, tertiary butyl alcohol, methanol and isopropyl alcohol, which is preferably purged from the system.
  • the pressure at the top of the sixth distillation column 60 may suitably be 0.7 - 7 kPa and the temperature may suitably be 32°C - 55°C.
  • the pressure at the bottom of the distillation column 60 may suitably be 0.7 - 8 kPa and the temperature may suitably be 150°C - 205°C.
  • the heavier distillation fraction 62 which comprises the alkylene glycol extractive distillation agent is charged to the fifth distillation column 50 in order to provide for the extractive distillation agent required therein.
  • a portion of the alkylene glycol extractive distillation agent in the line 62 may be routed by a branch line 61 controlled by a valve 63 to the extractive distillation charge line 56 for the first extractive distillation column 10.
  • a portion of the fraction 62 may be purged from the system by a branch purge line 66 controlled by a valve 68.
  • Fresh alkylene glycol extractive distillation agent may be added to the system, as needed, by a charge line 67 controlled by a valve 69 that is located downstream from the purge line 66.
  • a seventh feedstock comprising the third lighter distillation fraction 34 and the fourth heavier distillation fraction 46 may suitably be charged by way of a line 72 to a seventh distillation column 70 which may comprise, for example, from 30 to 50 theoretical trays and wherein the seventh feedstock is introduced at least 20 theoretical trays from the bottom of the column.
  • Distillation conditions are adjusted within the distillation column 70 to provide for the recovery of a seventh lighter distillation fraction 74 comprising acetaldehyde, methyl formate, propylene oxide, hexenes, methanol and a minor amount of C 8 to C 10 alkane and a seventh heavier distillation fraction 76 comprising substantially all of the C 8 to C 10 alkane extractive distillation agent charged to the distillation column 70 by the line 72.
  • the distillation conditions established in the sixth distillation column 60 may include a pressure at the top of the column of 105 - 200 kPa and a temperature of 38°C - 60°C and a pressure at the bottom of the column of 140 - 275 kPa and a temperature of 90°C - 150°C.
  • the C 8 -C 10 extractive distillation agent in line 76 may be recycled to extractive distillation charge lines 32 and 42 for columns 30 and 40, respectively.
  • the first heavier distillation fraction 18 is separated in sixth distillation column 60 into a heavier fraction 62 comprising the triethylene glycol extractive distillation agent which is charged to the extractive distillation column 50 and a lighter overhead fraction 64 comprising propylene oxide, water, acetone, tertiary butyl alcohol, methanol and isopropyl alcohol that is discharged from the system.
  • a second feedstock comprising the lighter distillation fraction 16 is separated in the second distillation column 20 - into 1005 parts of a heavier distillation fraction 24 and 1 part of a lighter distillation fraction 22 containing propylene, propane, acetaldehyde, pentenes and pentanes.
  • the second heavier distillation fraction 24 discharged from the distillation column 20 will comprise substantially all of the propylene oxide, water, hexenes and hexanes and heavier oxygen-containing impurities.
  • This fraction is charged by way of the line 24 to a third distillation column 30 together with 5620 parts of octane charged to the distillation column 30 by a line 32.
  • the distillation column 30 is operated in the manner described above to provide a lighter distillation fraction 34 ( 1 part) and a heavier distillation fraction 33 ( 6624 parts).
  • the fraction 34 will comprise acetaldehyde, methyl formate, methanol, water and residual quantities of propylene oxide and octane.
  • the third heavier distillation fraction 33 will comprise propylene oxide, water and substantially all of the octane charged to the third distillation column 30.
  • a fourth feedstock comprising a third heavier distillation fraction 33 is charged to the fourth extractive distillation column 40 where it is separated together with 3690 parts of octane in the manner described above into 1005 parts of an overhead distillation fraction consisting essentially of propylene oxide and water.
  • a heavier distillation fraction 46 discharged from the column 40 will comprise about 9309 parts of octane, hexenes, hexanes and residual quantities of propylene oxide.
  • a fifth feedstock comprising the fourth lighter distillation fraction 44 (about 1005 parts) together with 180 parts of triethylene glycol is charged to the column 50.
  • the fifth feedstock is separated in the fifth distillation column 50 into a fifth lighter overhead distillation fraction consisting essentially of propylene oxide (965 parts) and a fifth heavier distillation fraction 56 comprising 180 parts of triethylene glycol, 20 parts propylene oxide and water.
  • the fifth heavier distillation fraction 56 is charged to first distillation column 10 to provide the extractive distillation required therein and to provide for recovery of the propylene oxide contained therein.
  • the residual C 8 to C 10 alkane hydrocarbon extractive distillation agent discharged from the column 30 by the line 34 and the C 8 to C 10 alkane hydrocarbon discharged from the column 40 by the line 46 may be charged by line 72 to seventh distillation column 70 where it is resolved into a lighter distillation fraction 74 comprising impurities and a heavier distillation fraction 76 comprising the C 8 -C 10 alkane distillation agent which is recycled through the distillation columns 30 and 40 by extractive distillation charge lines 32 and 42, respectively.
  • a computer simulation of the distillation column 50 was conducted using a feedstock consisting essentially of propylene oxide contaminated with .005 wt.% of water.
  • propylene oxide feed was charged to the distillation column 50 through the line 44 at the rate of about 10,000 l/hr at a temperature of 45°C and a pressure of 650 kPa.
  • Triethylene glycol was charged by way of line 62 at the rate of 2,000 l/hr at a temperature of 45°C and a pressure of 650 kPa.
  • the column 50 was operated at a pressure of 175 kPa, a bottom temperature of 95°C, a top temperature of 38°C and a feedstock ratio of 1:1.

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Claims (6)

  1. Ein Verfahren zur Reinigung von rohem Propylenoxid, das mit geringen Mengen Wasser, C5- und C6-Kohlenwasserstoffen und sauerstoffhaltigen Verunreinigungen verunreinigt ist, welches die Schritte umfaßt:
    Extraktivdestillation besagten rohen Proyplenoxids in der Gegenwart eines C2- bis C6-Alkylenglykol-Exraktionsmittels in einer ersten Extraktivdestillationszone unter Extraktivdestillationsbedingungen, die so ausgewählt sind, daß sie eine erste niedriger siedende Destillationsfraktion, die Propylenoxid, Wasser und besagte kohlenwasserstoff- und sauerstoffhaltigen Verunreinigungen umfaßt, und eine erste höher siedende Destillationsfraktion, die besagtes Extraktionsmittel und einen Teil des im rohen Propylenoxids vorhandenen Wassers umfaßt, liefern;
    Destillation besagter ersten niedriger siedenden Destillationsfraktion in einer zweiten Destillationskolonne, einer dritten Extraktivdestillationskolonne und einer vierten Extraktivdestillationskolonne in der Gegenwart eines C8-C10-Alkankohlenwasserstoff-Extraktionsmittels, um besagte kohlenwasserstoff- und sauerstoffhaltigen Verunreinigungen zu entfernen und eine vierte Destillationsfraktion zu liefern, die im wesentlichen aus Propylenoxid und einer geringen Menge Wasser besteht; und
    Extraktivdestillation besagter vierten Fraktion in einer fünften Destillationskolonne in der Gegenwart eines C2-C6 Alkylenglykol-Extraktionsmittels unter Destillationsbedingungen, die so ausgewählt sind, daß sie eine abschließende fünfte niedriger siedende Destillationsfraktion, die im wesentlichen aus entwässertem Propylenoxid besteht, und eine abschließende fünfte höher siedende Destillationsfraktion, die besagtes Extraktionsmittel, Wasser und eine geringe Menge Propylenoxid umfaßt, liefern.
  2. Ein Verfahren nach Anspruch 1, wobei die höher siedende abschließende fünfte Destillationsfraktion zu besagter ersten Extraktivdestillationskolonne rückgeführt wird.
  3. Ein Verfahren nach Anspruch 1 oder Anspruch 2, wobei die Destillationsbedingungen in der ersten Destillationskolonne eine Bodentemperatur von 150°C - 200°C, einen Bodendruck von 140 - 345 kPa, eine Temperatur nahe dem Kopf der ersten Destillationskolonne von 26°C - 50°C, einen Druck nahe dem Kopf der Kolonne von 105 - 174 kPa und ein Verhältnis von rohem Propylenoxid zu besagtem C2-C6-Alkylenglykol von 2 - 7 einschließen und wobei die Destillationsbedingungen in besagter fünften Destillationskolonne eine Temperatur nahe dem Boden besagter fünften Destillationskolonne von 90°C - 105°C, einen Druck nahe dem Boden besagter fünften Destillationskolonne von 140 - 345 kPa, eine Temperatur nahe dem Kopf besagter Destillationskolonne von 30°C - 50°C, einen Druck nahe dem Kopf besagter fünften Destillationskolonne von 105 - 175 kPa und ein Verhältnis von besagter zweiten höher siedenden Destillationsfraktion zu besagtem C2-C6-Alkylenglykol-Extraktionsmittel von 4 bis 6 einschließen.
  4. Ein Verfahren nach Anspruch 1 zur Abtrennung verunreinigter Mengen von Hexenen, Hexanen, Pentenen, Pentanen, Wasser und sauerstoffhaltigen Verunreinigungen aus unreinem Propylenoxid, welches umfaßt:
    Extraktivdestillation des unreinen Propylenoxids in der ersten Destillationskolonne, um eine erste Überkopffraktion zu bilden, die Propylenoxid, Wasser, Hexene, Hexane, Pentene, Pentane, Wasser, Methanol und sauerstoffhaltige Verunreinigungen, die oberhalb von Propylenoxid sieden, umfaßt;
    Fraktionieren der ersten Überkopf fraktion in einer zweiten Destillationskolonne, um eine zweite Überkopffraktion, die im wesentlichen die gesamten Pentane und Pentene und den Großteil der sauerstoffhaltigen Verunreinigungen, die oberhalb von Propylenoxid sieden, umfaßt, und eine teilweise gereinigte zweite Propylenoxid-Bodenfraktion, die Propylenoxid, Wasser, Hexene und Hexane umfaßt, zu erhalten;
    Extraktivdestillation der teilweise gereinigten zweiten Bodenfraktion in einer dritten Destillationskolonne unter Verwendung eines C8-C10-Alkankohlenwasserstoff-Extraktionsmittels, um eine weiter gereinigte dritte Bodenfraktion zu liefern, die im wesentlichen das (die) gesamte(n) Propylenoxid, Wasser, Hexene und Hexane, die der dritten Destillationskolonne zugeführt worden sind, umfaßt;
    Extraktivdestillation der weiter gereinigten dritten Bodenfraktion in einer vierten Destillationskolonne unter Verwendung eines C8-C10-Alkankohlenwasserstoff-Extraktionsmittels, um eine zusätzlich gereinigte vierte Propylenoxid-Überkopffraktion zu liefern, die im wesentlichen aus Wasser und von besagten Verunreinigungen freiem Propylenoxid besteht; und
    Extraktivdestillation der vierten Propylenoxid-Überkopffraktion in einer fünften abschließenden Destillationskolonne unter Verwendung eines C2-C6-Alkylenglykol-Extraktionsmittels, um eine fünfte Überkopffraktion zu bilden, die im wesentlichen aus Propylenoxid besteht.
  5. Ein Verfahren nach Anspruch 1 zur Reinigung von rohem Propylenoxid, das mit Verunreinigungen verunreinigt ist, die Wasser, Propylen, Propan, Acetaldehyd, Methylformiat, Propionaldehyd, Hexene, Hexane, Aceton, Methanol, tert.-Butylalkohol, Pentan, Isopentan, Pentene, Isopropylalkohol und tert.-Butylformiat einschließen, welches die Schritte umfaßt:
    Zuführen besagter rohen Propylenoxid-Charge zu einer ersten Extraktivdestillationskolonne;
    Zuführen eines C2-C6-Alkylenglykol-Extraktionsmittels zu besagter ersten Extraktivdestillationskolonne an einem Zuführpunkt cberhalb des Punktes der Einführung von besagtem unreinen Propylenoxid:
    Fraktionieren besagten rohen Propylenoxids in besagter ersten Extraktivdestillationskolonne unter Destillationsbedingungen, die so ausgewählt sind, daß sie eine erste niedriger siedende Destillationsfraktion, die Propylenoxid, Propylen, Propan, Acetaldehyd, Methylformiat, Hexene, Hexane, Pentene und Pentane, Methanol und Wasser enthält, und eine erste höher siedende Destillationsfraktion, die im wesentlichen das gesamte Propionaldehyd, Aceton, tert.-Butylalkohol, tert.-Butylformiat, Isopropylalkohol, den Rest des Methanols und Wassers und im wesentlichen das gesamte Extraktionsmittel enthält, liefern;
    Zuführen einer zweiten Charge, die besagte erste niedriger siedende Destillationsfraktion umfaßt, zu einer zweiten Destillationskolonne;
    Fraktionieren besagter zweiten Charge in besagter zweiten Destillationskolonne unter Destillationsbedingungen, die so ausgewählt sind, daß sie eine zweite niedriger siedende Destillationsfraktion, die Wasser, das (die) gesamte(n) Propylen, Propan, Acetaldehyd, Pentane und Pentene und eine Restmenge Propylenoxid enthält, und eine zweite höher siedende, teilweise gereinigte Destillationsfraktion, die Propylenoxid, Wasser, Hexene und Hexane umfaßt, liefern;
    Zuführen einer dritten Charge, die besagte zweite höher siedende Destillationsfraktion umfaßt, zu einer dritten Extraktivdestillationskolonne;
    Zuführen eines C8-C10-Alkankohlenwasserstoff-Extraktionsmittels zu besagter dritten Extraktivdestillationskolonne an einem Zuführpunkt oberhalb des Punktes der Einführung von besagter dritten Charge;
    Fraktionieren besagter dritten Charge in besagter Extraktivdestillationskolonne unter Destillationsbedingungen, die so ausgewählt sind, daß eine dritte weiter gereinigte, niedriger siedende Destillationsfraktion, die Wasser und im wesentlichen das gesamte Acetaldehyd, Methylformiat und Methanol und Restmengen von Propylenoxid und Octan enthält, und eine dritte höher siedende Destillationsfraktion, die Wasser, im wesentlichen das gesamte Propylenoxid und Extraktionsmittel, die besagter dritten Destillationskolonne zugeführt worden sind, und im wesentlichen die gesamten Hexene und Hexane, die besagter dritten Destillationskolonne zugeführt worden sind, enthält, liefern;
    Zuführen einer vierten Charge, die besagte dritte höher siedende Destillationsfraktion umfaßt, zu einer vierten Extraktivdestillationskolonne;
    Zuführen eines C8-C10-Alkankohlenwasserstoff-Extraktionsmittels zu besagter vierten Extraktivdestillationskolonne an einen Zuführpunkt oberhalb des Punktes der Einführung von besagter dritten Charge;
    Fraktionieren besagter vierten Charge in besagter vierten Extraktivdestillationskolonne unter Destillationsbedingungen, die so ausgewählt sind, daß sie eine vierte niedriger siedende, zusätzlich gereinigte Zwischendestillationsfraktion, die im wesentlichen aus Propylenoxid und Wasser besteht, und eine vierte höher siedende Destillationsfraktion, die im wesentlichen das (die) gesamte(n) Extraktionsmittel, Hexene und Hexane, die besagter dritten Destillationskolonne zugeführt worden sind, und auch Restmengen von Propylenoxid enthält, liefern;
    Zuführen einer fünften Zwischencharge, die besagte vierte niedriger siedende Destillationsfraktion umfaßt, zu einer fünften Extraktivdestillationskolonne, Zuführen eines C2-C6-Alkylenglykol-Extraktionsmittels zu besagter fünften Extraktivdestillationskolonne an einem Zuführpunkt oberhalb des Punktes der Einführung von besagter vierten Charge; und
    Fraktionieren besagter fünften Charge in besagter fünften Extraktivdestillationskolonne unter Extraktivdestillationsbedingungen, die so ausgewählt sind, daß sie eine fünfte niedriger siedende Destillationsfraktion, die im wesentlichen aus Propylenoxid besteht, und eine fünfte höher siedende Destillationsfraktion, die Wasser, Extraktionsmittel und Restmengen von Propylenoxid umfaßt, liefern, und Rückführen besagter fünften höher siedenden Destillationsfraktion zu besagter ersten Destillationskolonne.
  6. Ein Verfahren nach Anspruch 5, wobei die siebte Charge, die besagte dritte niedriger siedende Destillationsfraktion und besagte vierte höher siedende Destillationsfraktion umfaßt, einer siebten Destillationskolonne zugeführt wird; und
    wobei besagte siebte Charge in besagter siebten Destillationskolonne unter Destillationsbedingungen fraktioniert wird, die so ausgewählt sind, daß sie eine siebte niedriger siedende Destillationsfraktion, die Wasser und im wesentlichen das (die) gesamte(n) Acetaldehyd, Methylformiat, Propylenoxid, Hexene und Methanol und einen geringen Teil des C8-C10-Alkankohlenwasserstoffs, die der siebten Destillationskolonne zugeführt worden sind, enthält, und eine siebte höher siedende Destillationsfraktion, die im wesentlichen das gesamte C8-C10-Alkan-Extraktionsmittel, das zur dritten und vierten Destillationskolonne zugeführt worden ist, enthält, liefern, und wobei besagte siebte höher siedende Destillationsfraktion zu besagter dritten und vierten Destillationskolonne als besagte dritte und vierte Extraktionsmittel rückgeführt wird.
EP94306848A 1993-09-23 1994-09-19 Mehrstufiges Verfahren zum Trocknen und Reinigen von Propylenoxid Expired - Lifetime EP0645381B1 (de)

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US08/125,276 US5354431A (en) 1993-09-23 1993-09-23 Plural stage drying and purification of propylene oxide
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DE69406751D1 (de) 1997-12-18

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